Morphological identification and characterization of the formation of floral primordium in Vanilla planifolia (Orchidaceae)

Objective: To morphologically identify and characterize the formation of floral primordium and the individual flower development in Vanilla planifolia Jacks Ex. Andrews. Design/Methodology/Approach: Inflorescence primordia and young inflorescences in different development stages were sampled from the stem internodes of the following positions: basal (11-15), middle (6-10), and distal (1-5). Four samples were taken from each stem position from February to May, with five repetitions per sampling date. Observations and characterization were made with a stereo microscope. The study site was located at Rancho Xanathtlan, in Barriles, municipality of Gutiérrez Zamora, Veracruz. Results: The development of the V. planifolia raceme is described in seven phases: (I) differentiated meristem of the floral inflorescence; (II) appearance of the third bract; (III) initiation of the racemes formation; (IV) elongation of the floral primordium; (V) development and growth of the individual floral primordium in the acropetal direction, (VI) anthesis of the inflorescence in the acropetal direction; and (VII) complete flowering of the raceme. The development of the buds in the raceme is described in five stages from the appearance of the third bract in the acropetal direction. Study Limitations/Implications: The biochemical processes and the interaction of environmental aspects on the floral development of V. planifolia pose questions that remain unanswered. Findings/Conclusions: The first aspects of floral formation within the inflorescence of Vanilla planifolia were determined, along with its floral phenology.